Cyclic nucleotide metabolism is being studied in lymphocytes from patients with chronic lymphocytic leukemia and other disorders characterized by aberrant lymphocyte function. Cyclic AMP levels and adenyl cyclase activity are being assayed, and the response to prostaglandin E1 and beta-adrenergic stimulators is being assessed. The experiments are aimed at further exploring the possible role of cyclic AMP as a mediator of cell growth and differentiation, by examining its activity in "experiments of nature" in which these cellular functions are abnormal.